The mother during pregnancy and the puerperium: Detailed data abstracted from the clinical obstetric records of ALSPAC pregnancies

Background When the Avon Longitudinal Study of Parents and Children (ALSPAC) was planned, it was assumed that the clinical obstetric data would be easily accessible from the newly developed National Health Service computerised ‘STORK’ system. Pilot studies, however, showed that, although fairly accurate in regard to aspects of labour and delivery, it was, at the time (1990-2), inadequate for identifying the full antenatal and postnatal details of clinical complications and treatments of the women in the Study. Methods A scheme was therefore developed to train research staff to find and abstract relevant details from clinical records onto proformas designed for the purpose. Extracting such data proved very time consuming (up to six hours for complicated pregnancies) and consequently expensive. Funding for the enterprise was obtained piecemeal using specific focussed grants to extract data for subsamples of the Study, including a random sample to serve as controls. Results To date, detailed records have been completed for 8369 pregnancies, and a further 5336 (13,705 in total) have complete details on specific prenatal areas, including serial measures of maternal blood pressure, proteinuria and weight. In this Data Note we describe the information abstracted from the obstetric medical records concerning the mother during pregnancy, labour, delivery and the first two weeks of the puerperium. Information abstracted relating to the fetus (including fetal monitoring, presentation, method of delivery) and neonate (signs of asphyxia, resuscitation, treatment and well-being) have been described in a further Data Note. Conclusions These data add depth to ALSPAC concerning ways in which the signs and symptoms, procedures and treatments of the mother prenatally, intrapartum and postnatally, may impact on the long-term health and development of both mother and child. They augment the data collected from the mothers’ questionnaires (described elsewhere) and the ‘STORK’ digital hospital data.

To date, detailed records have been completed for 8369 pregnancies, and a further 5336 (13,705 in total) have complete details on specific prenatal areas, including serial measures of maternal blood pressure, proteinuria and weight.In this Data Note we describe the information abstracted from the obstetric medical records concerning the mother during pregnancy, labour, delivery and the first two weeks of the puerperium.Information abstracted relating to the fetus (including fetal monitoring, presentation, method of delivery) and neonate (signs of asphyxia, resuscitation, treatment and well-being) have been described in a further Data Note.

The rationale
The Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC -later renamed Avon Longitudinal Study of Parents and Children) was specifically designed to identify, inter alia, the possible adverse or beneficial effects of environmental features on the development and health of the child.Particular attention was paid to the pregnancy and the first year of life; the environment was defined as anything (other than genes) that might have an effect, as the developing fetus was especially sensitive to change during this period.Consequently, as pregnancy was known to be important for development of organs such as the brain, it was decided to obtain as much information as possible for this period.It was clear that the pregnant woman herself was best able to report on various environmental exposures to herself when at home, but it was not clear that she would be able to report accurately on the clinical progress of her pregnancy, including the investigations, diagnoses, medications and other treatments she may have undergone as part of antenatal and inpatient care.

Designing the data collection tool
There were a number of influences on the design of the data that have been collected.These were partly based on reviews of the literature to identify factors thought to influence the development of the child, and information collected in other studies of birth cohorts (e.g. the 1958 and 1970 National UK birth cohort studies), but the major influences (particularly in regard to recording data relevant to the hypertensive disorders of pregnancy) were those developed by Jean Golding and colleagues for (a) the International Study of the Hypertensive Disorders of Pregnancy funded by WHO (World Health Organisation), which took place in a number of developing countries including Thailand, Vietnam and China (Golding et al., 1988); and (b) The Jamaica Low Dose Aspirin Study (Golding et al., 1998).
The latter studies showed the importance of collecting the actual measurements (e.g. of blood pressure, proteinuria, haemoglobin) rather than relying on clinical diagnoses which were likely to vary with the clinician/hospital/country.This background dictated the importance of abstracting as many measurements as possible, as well as details of investigations and treatments.The data abstraction form (Birmingham et al., 2021a), with the instructions to the Data Abstractors (Birmingham et al., 2021b) and checkers (Birmingham et al., 2021c) have been made available (see Extended data).

Structure of the obstetric services in Avon 1990-2
The Study area (defined as that part of the county of Avon within the South West Regional Health Authority, hereinafter referred to as Avon (Boyd et al., 2019)) was served by consultant obstetric services based in the two major obstetric teaching hospitals within Bristol: Southmead Hospital and the Bristol Maternity Hospital (BMH) (subsequently known as St Michael's Hospital).In addition, deliveries of low-risk pregnancies were undertaken at Weston General Hospital (WGH) situated in Weston-super-Mare.There were dedicated neonatal intensive care and special care baby units at BMH and Southmead but not at WGH.All pregnancy and delivery care

Amendments from Version 1
The paper has been amended in order to update the references to relevant Data Notes that were referred to but not published at the time of the previous version of the paper.In particular, the Abstract (last two paragraphs); further clarification added to Features of Pregnancy/Conception (last sentence); Medical Complications of pregnancy; Other details of pregnancy; and additional references.At the end of the Discussion, we have expanded on the potential use of the data in assessing the safety (or otherwise) of the medications and procedures to the child during pregnancy, or while breast feeding, as well as the possible effects on the mother herself.
Any further responses from the reviewers can be found at the end of the article was free as part of the National Health Service (NHS), and private practitioners were used rarely by the Avon maternity population.
Antenatal care was undertaken by general practitioners (GPs) and community midwives.For most pregnancies, one of the consultant obstetricians would also have been involved and, provided he/she was happy that the woman was not of very high risk, she would have had "shared care".Very few women intended to have a home delivery.
Thus, for women enrolled in ALSPAC, the system for antenatal care in those at low risk involved shared care between hospital-based consultant obstetricians and midwives based in the community and working with the woman's GP.Women at high risk of complications would be more likely to have been seen throughout their pregnancy by the clinical obstetric services, mainly within the relevant hospital, although some obstetricians visited community clinics, particularly those based in areas of deprivation.
The contemporary protocols concerning care used by the medical staff at each of the three hospitals have been added to the ALSPAC archive as part of the University of Bristol Special Collections [Box 784].These protocols should be used with caution as there is evidence that these guidelines were not always adhered to.
The hand-written clinical measurements and observations made in the community and those made in hospital were all paper records and filed by each hospital in a single folder, with the exception of fertility and psychiatric records, which were kept separately.Important information could be found in many different places within the records, having been documented variously by medical and nursing/midwifery staff.This required meticulous systematic scrutiny in order to abstract accurate data.Details of all pregnancy-related hospital admissions were also included in the record.For complex pregnancies the folder could be as thick as 6-8 inches, comprising A4-sized paper, frequently handwritten on both sides, as well as laboratory results on flimsy print outs.
The STORK digital record of pregnancy and delivery had been initiated in the two major hospitals shortly before the start of the enrolment of the pregnant women in ALSPAC.Comparison of the data collected with the information desired showed that the information in the computerised record was reasonably accurate for many features of labour and delivery, but it lacked the fine detail, particularly in regard to antenatal and postnatal information -including the repeat measures such as of weight and blood pressure.The ALSPAC team reluctantly decided therefore to collect all relevant data by hand from the medical records.

Methods and materials
ALSPAC was designed to assess the ways in which the environment interacts with the genotype to influence health and development (Boyd et al., 2013;Fraser et al., 2013).Pregnant women resident in the Study area with an expected date of delivery between 1 st April 1991 and 31 st December 1992, were invited to take part.About 80% of the eligible population did so.The initial ALSPAC sample consisted of 14,541 pregnancies; of these initial pregnancies, there was a total of 14,676 fetuses, resulting in 14,062 live births and 13,988 children who were alive at one year of age.Information on the cohort parents and their offspring was collected using a variety of methodologies including self-completion questionnaires sent to Study mothers, fathers, teachers and the Study child, direct examination under standardized conditions, and linkage to other medical information from NHS records and educational data from the school systems.Please note that the Study website contains details of all the data that is available through a fully searchable data dictionary and variable search tool (http://www.bristol.ac.uk/alspac/researchers/our-data/).
Ethical approval for the study was obtained from the ALSPAC Ethics and Law Committee (ALEC; IRB00003312) and the NHS Local Research Ethics Committees (LREC) (Birmingham, 2018).Detailed information on the ways in which confidentiality of the cohort is maintained may be found on the Study website: http://www.bristol.ac.uk/media-library/sites/alspac/ documents/pearl/CO90S_linkage_detailed.pdf and details of all NHS Research Ethics approvals: http://www.bristol.ac.uk/medialibrary/sites/alspac/documents/governance/Research%20Ethics %20Committee%20approval%20references.pdf.

The subsample strategy
Unfortunately, for the first 10 years of the Study there was no designated core funding available, and ALSPAC survived by including a 'fee' in each grant application to contribute towards the funding of the central running of the Study.The initial funding obtained for ALSPAC was used for costs that could not be postponed: collection of contemporary information from mothers and their partners, as well as for processing and storage of biological samples.The obstetric records could be accessed and abstracted as and when funding became available.Although unavoidable, there was a major disadvantage with this strategy in that the relevant hospitals became short of storage space for records, and they were, by 2006, held on 19 different sites.Consequently, searching for any particular record took an average of two hours.
In parallel, some obstetric records were also stored in non-paper formats (optical discs or microfiche).Electronic tracing of hospital records was inefficient, with the systems frequently inaccurate and not kept up to date.Extensive knowledge of both the computer systems and physical environment was necessary to locate the records.Double or triple registration with equivalent sets of notes was not uncommon after a merger of two of the hospitals' records departments.
Data abstraction is expensive primarily because it is extremely time consuming.ALSPAC was unable to obtain funding to extract the full set of detailed obstetric records relevant to all pregnancies in the Study.The fall-back position was to use parts of grants for specific projects and consequently the abstraction of many of the obstetric and neonatal records was funded using three types of funding sources: (a) specific project grants for the purpose; (b) as a small part of the 'core funding' from the Medical Research Council (MRC) and the Wellcome Trust after the year 2000, and (c) using portions of the 'ALSPAC fee' of the project grants obtained for ALSPAC in the early years of the Study.Below are listed the eight grants with funding for specific abstraction from the obstetric records.
(1) Twins in a natural experiment to study causes of language delay; Jean Golding (PI), Michael Rutter, Karen Thorpe; Funder: Mental Health Foundation.
(2) Twins in a natural experiment to study causes of language delay; Jean Golding (PI), Karen Thorpe, Sue Roulstone; Funder: South West Regional Health Authority R & D.
(3) The association between different types of antenatal care and the mother's anxiety and depression levels; Jean Golding (PI), David Jewell, Lindsay Smith, Ian MacGillivray, Helen Francomb; Funder: South & West Regional Health Authority.
(4) Obstetric and medical consequences of teenage pregnancy; David Jewell (PI); Jean Golding; Funder: (5) Evidence of the long-term consequences of caesarean section is required to allow informed maternal choice; Gordon Stirrat (PI), Jean Golding; Funder: Bupa Foundation.

Definition of the subsamples
As a result of the funded grants and the funding restrictions, to date only 8369 pregnancies have undergone selection for the detailed data abstraction using the proforma shown in the data abstraction form (see Extended data (Birmingham et al., 2021a)).The different selection criteria are described below.
(i) Twins and closely spaced singletons: This study compared the development of twin pairs with singletons with a closely spaced sibling.Abstraction of the obstetric and neonatal records was to test whether delay in twin development of speech was related to obstetric problems in pregnancy or whether it concerned the difficulties mothers had in relating to two similarly aged siblings; 94 twin pregnancies were compared with 97 pregnancies where there was a sibling born within 30 months of the Study child (Rutter et al., 2003).
(ii) All multiple pregnancies: After completion of the selection of the twins for the Rutter study, it was decided for completion to extract details of all remaining multiple pregnancies, regardless of the outcome of pregnancy (n = 188 in total).
(iii) All fetal and neonatal losses: These data will be described in the neonatal Data Note.
(iv) Cerebral palsy and missing twins: The children with diagnosed cerebral palsy were identified through the Community Child Health system.Only those with a Study placenta available were selected.This was part of the study headed by Peter Pharaoh (see above) to determine whether there was any evidence of a missing twin among children with cerebral palsy.
In addition, we identified from the maternal questionnaires administered at 18 weeks gestation and two months post-delivery all those instances where the mother had indicated that, during pregnancy, she had been informed that she had, or might have had, a multiple pregnancy, but in fact she delivered a singleton.
[The placentas of all in this group (n=67) were examined for signs of a missing twin as were their controls (n=124) and children with cerebral palsy who had placentas available (n=18)].The results were largely negative and never published.
(v) Delivered preterm: In order to determine an accurate preterm delivery rate within ALSPAC, all deliveries with gestation <37 weeks identified using any of: mother's stated estimated date of delivery (EDD), EDD based on date of last menstrual period (LMP), gestation on STORK, and obstetrician's estimates of gestation were considered.If there was consistency between two or more records, the records were not selected for review and the delivery was judged to be preterm.If some estimates were <37 completed weeks and others were not, the records were obtained and the data abstracted, and a decision made by a consultant obstetrician using the clinical information in the notes, including the results from early ultrasound scans.This resulted in identification of two groups of pregnancies -one of definite preterm delivery (those of <36 weeks agreed by all sources; n = 480), and the other of possible preterm delivery upon which the decision had been made (<37 completed weeks n = 1022).These data were used to identify the ALSPAC preterm delivery rate as 5.5% (Little et al., 2004).
(vi) Teenage mothers: ALSPAC pregnancies to women aged <20 years at the time of delivery (n = 645).
( (xii) Deliveries outside of Avon hospitals: This group includes home deliveries, babies born before arrival at the hospital or delivered in hospitals outside the Avon area.These records were abstracted since it was likely that they would be difficult to find in the future (n=352).
(xiii) Random sample: The random sample was selected from the complete set of ALSPAC births for the depression study by the statistician Jon Heron.This selection was expanded as the other sections were completed.The selection includes (but is not confined to) pregnancies that appear within other sections (n=2760).
It is important to note that, in general, the data abstractors were not aware as to which group the pregnancy was in.This of course would have been obvious to them once they had accessed the medical records for selections on the type or place of delivery, teenage pregnancies, twins or preterm deliveries, but selections based on maternal depression or specific child outcomes were not revealed to them and they were blind as to whether the records concerned a specified group or the random control group.

Abstraction and checking of information
As already noted, the data abstractors used a paper proforma which was identical for all subgroups (with the exception of the twin sample) on which to detail the information from the medical records (Extended data (Birmingham et al., 2021a)), rather than keying straight onto a digital form.This was because, for the most part, the medical records had little structure, particularly for women with complex histories including several hospital admissions during the pregnancy.Key pieces of information could be found in various entries and could be contradictory.Thus, the team who carried out the data abstraction had to be skilled in the recognition of source and validation of various items of information.They mainly had a background in midwifery and/or nursing.The relevant instructions to the data abstractors (including how to resolve contradictory information); definitions of the items to be recorded are shown in Extended data (Birmingham et al., 2021b).Each completed form was meticulously checked by another data abstractor without reference to the original records; instructions for such checks are shown in Extended data (Birmingham et al., 2021c).If queries or inconsistencies were unresolved, the records would be referred to again.These checks were made before the record folders were returned to the hospital record stores to prevent having to search for them a second time.
Once the forms had been completed and checked, the information was double keyed by an external bureau.There were two types of data -the data for which boxes had been ticked or numbers filled in (such as dates and the results of tests), and other details that were keyed in-house as text.The text is available for coding by those with particular interests, on application to the ALSPAC Executive.The more specific information is available and is summarised in Summary of the data available.

The variable numbering system
The variable numbers for most of this data set all start with the letters 'DEL_P' followed by a number.For simplicity this will be known as the P number throughout this paper.In addition, the question number is quoted -i.e. the actual question asked on the data abstraction form (Extended data (Birmingham et al., 2021a)), as well as to the instructions for the data abstractors, reproduced as Extended data (Birmingham et al., 2021b).The variable nomenclature differs, however, for data abstracted for the whole dataset (see The extended dataset abstraction), for the ultrasound scans (see Ultrasound scans) and the antenatal admissions (see Antenatal hospital extractions) although the form and instructions remain valid.

Suggested statistical analysis using the subgroup design
For analysis of the 8369 pregnancies, it is important to note the potential biases in ascertainment of some of the subgroups (see Definition of the subsamples).There are a number of alternative ways in which these could be addressed in statistical analyses, as suggested briefly below.
(a) If there is sufficient power, we recommend using the random sample only.
(b) An alternative is to include, with the truly random sample the randomly ascertained group of pregnancies with livebirths followed up as Children in Focus.
or (c) Combine all the groups and use conditional or unconditional analytic strategies taking account of the different groups (see Pearce ( 2016) for discussion of pros and cons).

Omissions from this Data Note
In this paper we have omitted information from the obstetric data abstraction that relates to the fetus or neonate.That information is described in a separate Data Note (Birmingham et al., 2021d) which concentrates on the details relevant to the fetus, the birth and the neonatal period.Thus, it describes separate records for each member of a multiple pregnancy, and includes details of fetal distress and gestation at delivery.

The extended dataset abstraction
Two grants awarded in 2006 (US National Institutes of Health [NIH]) and 2009 (Wellcome Trust) to DA Lawlor and colleagues provided funds to complete abstraction of certain data from the clinical obstetric records from all remaining eligible women.The selected data comprised ABO and Rhesus blood groups, and repeated measurements of weight, blood pressure, glycosuria, haemoglobin and proteinuria, but did not include many other antenatal, intrapartum and postnatal measurements, treatments or procedures.With this effort, data became available on a total of 13,706 women (13,899 offspring) with derived variables on hypertensive disorders of pregnancy, gestational diabetes, anaemia, and maternal weight gain.For analyses of these data there is no need to use the strategies described under Suggested statistical analysis using the subgroup design since these data are available on the whole sample (http://www.bristol.ac.uk/alspac/external/documents/ALSPAC_Data_Dictionary.zip1 ; see also Lawlor et al., 2010;Macdonald-Wallis et al., 2012;Macdonald-Wallis et al., 2014;Macdonald-Wallis et al., 2015).

Summary of the data available
In this section we describe most of the data available on the ALSPAC Study pregnancies.For further details of the data see the file in the ALSPAC Data Dictionary: http://www.bristol.ac.uk/alspac/external/documents/ALSPAC_Data_Dictionary.zip2 .
Serial measures during pregnancy Ultrasound scans.At the time when the Study mothers were enrolled there was considerable discussion as to whether ultrasound scans were completely safe for the developing fetus -particularly for the child's subsequent development (Reece et al., 1990).For this reason, details of all ultrasound scans were collected.Data collected for each scan included: (a) gestation at which the scan was performed (calculated using the date of scan and the best clinical estimate of the EDD); (b) the reason for the scan; (c) the type of scan; and (d) the results of the scan (Table 1).
Among the 8369 women for whom the medical records data have been fully abstracted, 7945 (95%) had documentation for up to 33 scans occurring before the baby was born.The scans included those carried out in the community (usually in GP surgeries), in outpatient radiography clinics, and as part of inpatient care.All scans undertaken between conception and delivery were included.Any postpartum scans were excluded.or presence of two or more fetuses (once identified, any subsequent scans that merely confirmed twins were coded as normal).The descriptions of the abnormalities were described as text and have not been coded yet.
Antenatal hospital admissions.This section did not include admissions of mothers who were in labour on admission, only admissions during pregnancy before the onset of labour.In all 5715 women were admitted to hospital at some point before the start of labour (DEL_H050).The total no. of admissions per woman varied from 0 to 18 (DEL_H002), and the no. of days in total that the mothers stayed as an inpatient ranged from 1 to 80 (DEL_H001).
For each admission, coded information was collected on three items: the gestation at admission (in days), the number of days stayed and the hospital involved ( This data set has the advantage of using all the medical records that could be retrieved, and consequently can be used to identify prevalence.Lawlor's group have derived a number of useful variables including (a) maternal weight change between 0-18 weeks gestation (DEL_1128), (b) maternal weight change 18-28 weeks gestation (DEL_1129), maximum level

Features of pregnancy
Conception.Although data were collected on whether the pregnancy had resulted from fertility treatment, most of this information is coded as text, with the exception of in vitro fertilisation (IVF), which has been coded.Other sources of information on fertility treatment can be obtained from the maternal questionnaire D (for example variable D031 documents the methods used to help the woman conceive, and D032 identifies ovulation induction).The actual date of last menstrual period (LMP) was not recorded and is not available for confidentiality reasons.However, it was used for calculations of the various stages of gestation when events occurred.In contrast the month of LMP is available for analysis of seasonal effects.Whether or not the woman was certain of the date of her LMP was collected as an indicator of her personality as well as of a possible problem for the obstetric team (Table 4).
Planning for obstetric care.The type of antenatal care planned is given in DEL_P1003.Of the 8307 pregnancies with this information, 8089 (97%) were planned to have shared care, and only 218 had a different initial plan.At the first antenatal visit a plan was also made as to where the baby would be delivered.Table 5 summarises the initial intention compared with where they actually were delivered.

Medical complications of pregnancy.
Abstracted from the medical records were a number of specific conditions.The ALSPAC codes and numbers of women involved are shown in Table 6.It should be noted that a further source of information on bleeding, infections and other problems can be found in the maternally completed questionnaires B, C and E, which detail the episodes by trimester (see Ellis et al., 2022).

Results of standard laboratory tests during pregnancy.
The ABO and Rhesus blood groups of the women are shown in Table 7, and the presence of Rhesus antibodies, together with other biochemical results in Table 8.Procedures undertaken during pregnancy.With the exception of the straightforward ultrasound examinations (see Ultrasound scans), the most common procedures undertaken were biophysical profile, amniocentesis and giving anti-D to Rhesus negative women (Table 9).
Advice given to the pregnant woman.Only specific advice given during pregnancy and written as such within the notes are included in this section (Table 10).Further information written in the text is likely to expand on, for example, the type of diet recommended.
Other details of pregnancy.Information on all the various signs and symptoms occurring during pregnancy, together with information on medications taken were collected in three questionnaires completed by the mother and are available to view, with relevant frequencies among the Built Files as the A file (including gestation medication taken in early pregnancy), B file (for data relevant to the first 18 weeks of pregnancy), the C file (for the three months up to 32 weeks gestation), and the D file (for medication regularly taken) (see Ellis et al., 2022).The frequencies of the maternal report of the medication she had taken during pregnancy have also been published (Headley et al., 2004).

Labour and delivery
In this section we include aspects relating to the mother but not to the fetus/infant.As a rule of thumb, if the measures for one member of a multiple birth could be different (e.g.presentation at the onset of labour), then the data are described in a further Data Note on the fetus/neonate (Birmingham et al., 2021d).Although a complete distinction between the two is not feasible, we have tried to minimise the overlap.
In Table 11-Table 14 we describe the various procedures undergone, the methods used to induce and augment labour, the anaesthetics and analgesics used to reduce pain during labour and/or caesarean section, and the other medications administered.

Duration of the labour and delivery.
Many of the details concerning the length of time various birth processes took are shown in Table 15.The variables available include the length of time from membrane rupture to delivery, admission to delivery and the start of labour to delivery.It should be noted that where data are missing, valid information may be available in the STORK dataset (see Mummé et al., 2020).

Other noted features of labour.
There were a variety of different conditions noted in labour, including indications of preeclampsia (blood pressure, proteinuria, oedema), haemorrhage, pyrexia, ketonuria and maternal distress.In addition, position in labour as well as whether a water birth or blood transfusion    took place (Table 16).Nevertheless, there were a large number of descriptions written by the data abstractors which have not been coded as yet.They are available to the interested researcher, however.Notably, only 1147 (14%), of the 8369 women with detailed data abstractions had no complications during labour.

The mother in the puerperium
Conditions present in the puerperium.The NHS expectation at the time, after the mother had been discharged home, was for the community midwifery team to follow up the mother for the first 14 days after delivery.The midwife's notes were eventually included in the hospital record folder, and were thence available for scrutiny by the data abstractor, together with those notes made by the clinical team in hospital.From these records, information on the perineal consequences of delivery (episiotomy or tears), postpartum haemorrhage and anaemia were noted, markers of postpartum pre-eclampsia, deep vein thrombosis and pulmonary embolism, and other conditions including infections and procedures such as catheterisation and sterilisation (Table 17).

Medications taken postpartum.
A wide variety of drugs were administered to mothers post-delivery, including painkillers (varying from general anaesthetic and strong opiates to paracetamol), injected drugs to prevent haemorrhage (ergometrine, oxytocin (syntocinon) or a mixture of the two (Syntometrine)), antibiotics and a variety of other medications (Table 18).Out of the 8369 women, only 31 (0.4%) had no medications at all.It should be noted that mothers also recorded medications they took during this time period (see the E built file).In contrast to the antenatal medication records, these have not yet been coded but are available to the interested researcher.
Admission and discharge from hospital.The women stayed in hospital for a median of three days but a maximum of five weeks post-delivery.Once discharged 222 (2.6%) were  readmitted for a variety of reasons (Table 19).Further details of all women are available as text.

Discussion and conclusions
This paper demonstrates the wealth of data collected on 8369 pregnancies, selected for a variety of reasons, many of which result in a population weighted with high risk pregnancies; consequently, the pregnancies in this group include all those resulting in fetal/neonatal deaths, multiple births, caesarean sections, preterm deliveries, and cerebral palsy.Care needs to be taken when using these data alone.We are hoping to fill the gaps eventually.When (and if) further data are added, this Data Note will be updated.In the meantime, we have made some suggestions as to ways in which the current data could be analysed.
One of the major reasons why such detailed data were collected concerns the importance of being able to determine the long-term consequences of exposures to the fetus from medications and procedures undertaken during pregnancy as well as the possible consequences to the child of drugs given to the breast-feeding mother.Medications of potential importance include the anaesthetics and analgesics (e.g.opiates including Fentanyl) taken during labour, the drugs used to induce and augment labour (including prostaglandins and synthetic oxytocin), and the analgesic drugs given to the mother postnatally if she was breast feeding.Concerning procedures, long-term effects on the fetus of repeated ultrasound examinations have not, to our knowledge, been considered in the literature.
There is some evidence that ultrasound has a warming effect on certain tissues -and in theory this may result in damage  to the brain or other organ of the developing fetus.Among the 8369 women, the maximum number of scans recorded was 33.This was considerably above the recommendations at the time.
Little effort has been made to date to examine possible longterm effects although ALSPAC has collected a considerable repertoire of phenotypes on the offspring including neurocognitive, anthropometric, cardiovascular as well as biochemical, genetic and DNA methylation outcomes collected over time -including from the neonatal period through to age 30+.
Additional advantages of the detailed data collection described concern the ability to determine any long-term effects on the mothers themselves, since they have also been followed for 30 years since the study child was delivered.Analyses looking at early outcomes have demonstrated the advantages of the approach (e.g.Martin et al., 2022;Patel et al., 2007), but long-term documentation has yet to be undertaken.
It may be claimed that the pregnancies of 30 years ago will have no relevance today.However, there are two reasons for looking at the long-term effects of the features of the treatment of the mother as shown here: (i) even if a substance/procedure is no longer used, any long term effects (positive or negative) will add to basic biological knowledge, and (ii) if still being used, the study of these data will add to overall knowledge as to their safety (or the risks attached to their use) throughout the lives of the mother and her offspring.
The data described in this Data Note are confined to what was documented in the medical record.It is important to point out, however, that other relevant data are available including the computerised STORK data (Mummé et al., 2020), and the prospective data collected from the women during pregnancy and after delivery, using detailed self-report questionnaires administered at 18 and 32 weeks gestation as well as at eight weeks postpartum (Ellis et al., 2022).These provide information on a variety of signs and symptoms occurring during and after the pregnancy, together with the non-obstetric medications taken.

Strengths and limitations
There are four major strengths of these data.Firstly, each item was abstracted from the paper medical record with a strict protocol and meticulous checking; secondly, the data collected were documented at the time that the maternal examinations were undertaken, the treatments prescribed and the observations made, so that there was no element of retrospective recall; thirdly, these data can be augmented by information from the maternal questionnaires completed prenatally and postnatally on her signs and symptoms, procedures undertaken and medications taken, to provide a different aspect of the pregnancy; and fourthly, and importantly, the data provide an important baseline from which to assess the long-term benefits and possible hazards of the various facets of maternity care.
There is one major limitation of the data -which is that, with the exception of the important longitudinal information on blood pressure, weight and diabetes, the details on many aspects of maternal exposures and conditions are missing for over 5000 pregnancies.Admittedly, by the selection criteria used on the 8369, the majority of the more complex pregnancies have already been abstracted, but for valid epidemiological analysis the population of all 'normal' pregnancies are also needed.It is hoped that efforts can be made in the future to fill this important gap.
1. Please read the ALSPAC access policy which describes the process of accessing the data and samples in detail, and outlines the costs associated with doing so.
2. You may also find it useful to browse our fully searchable research proposal database which lists all research projects that have been approved since April 2011.
3. Please submit your research proposal for consideration by the ALSPAC Executive Committee.You will receive a response within 10 working days to advise you whether your proposal has been approved.
Figshare: ALSPAC Mother during pregnancy and the puerper-ium_ abstraction checking instructions.https://doi.org/10.6084/m9.figshare.13621703(Birmingham et al., 2021c).As mentioned by the authors, the initial ALSPAC sample consisted of 14,541 pregnancies, 14,062 live births and 13,988 children who were alive at one year of age.This is a reasonably large population that included 80% of eligible pregnant women.The documented experience of these women and the obstetric care they received in 1990-92 (including the medications, ultrasound exposure, pregnancy complications, etc) could provide scientific insights to questions that may or may not be obvious today.
Data collected on some maternal factors (such as blood groups, weight, blood pressure, glycosuria, haemoglobin, proteinuria and related derived variables) are available on a total of 13,706 women (13,899 offspring).However, complete information from medical records is currently available for only a sample of 8,369 pregnancies.The availability of information on a selected (non-random) subset of the cohort will present a challenge to some researchers.This limitation is acknowledged clearly by the authors and it is hoped that availability of subsequent funding will permit addition of information on the remaining 5,336 pregnancies.Meanwhile, a clear understanding of the process by which records were selected for inclusion in the subsample (of 8,369 pregnancies) will allow researchers to use these data for answering specific questions in a valid manner.
Open access to the data from cohorts such as ALSPAC will enhance and facilitate scientific studies on clinical and epidemiologic issues.The authors are to be applauded for their efforts to make these data available for wider exploitation, and it is hoped that their current and future attempts to abstract information on the complete cohort are successful.

James Roberts
Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, PA, USA In general, the ALSPAC database is a remarkable resource despite some limitations.It was drawn from 14,000 pregnancies occurring between the 1st of April of 1991 and the 31st of December 1992.The strengths are the enormous amount of data that is available, and the excellent collection and checking strategies.It also seems that the information that has not been collected thus far has at least the possibility of being extracted from stored information in the future.Based on their ability to obtain funding they were able to complete the planned data assessment of about 8,000 of the 14,000 pregnancies that are available.They also, were able to augment the 8,000 plus patients with another 5,000 with some but not all the data that they had originally hoped to collect.This has been further augmented by other studies which examined certain variables in that were extracted for particular studies.In addition, the collection of the data, especially that of the 1st 8,000 patients is more heavily weighted towards pregnancies that are not normal.This is less so in the additional 4,000 pregnancies.They point out strategies to circumvent these limitations.
The weaknesses of the study are largely the failure to have a complete set of data on all patients.There is the hope in the future to extend the amount of data to include more normal patients in the future.Although it has never stated explicitly it seems that all the data which has not been collected is in theory potentially collectible in future studies.It would be helpful if this point had been made more clearly.The other evident weakness of the data is the fact that it was collected many years ago.This is, nonetheless, also a strength.The weakness is that obstetrical care patterns have changed, and general population characteristics (for example the frequency of obesity) have changed over time.However, although again not stated explicitly they apparently have the capacity to follow these mothers and infants even at this long time after pregnancy (it would be useful to make this clearer).That length of follow up to examine the impact of the huge amounts of data describing pregnancy and outcomes is available in almost no other setting.
In summary the database is a remarkable resource.It has limitations, but it does appear that many of these limitations can still be potentially overcome if sufficient funding was available.However, even in the form it exists it has remarkable amount of information well collected over a remarkable time span to answer many very important questions.

Is the rationale for creating the dataset(s) clearly described? Yes
Are the protocols appropriate and is the work technically sound?Yes

Are sufficient details of methods and materials provided to allow replication by others? Yes
Are the datasets clearly presented in a useable and accessible format?Yes Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Pregnancy, adverse outcomes in pregnancy, preeclampsia I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
I've got a number of comments: 1) It is baffling to read that abstraction of the records of babies born in the early 1990s is still ongoing and even more so that data abstraction in itself can take up to two hours per women.An unanswered question is whether the authors expect that another 10,000 hours will need to be spent on data abstraction for the more than 5,000 women who together with their babies are still not included in the ALSPAC cohort and when this will be completed.Related to this, I don't feel that the authors present enough evidence that this ongoing effort is still relevant.
2) I read little about the completeness and accuracy of the abstracted data.I assume that the approach was taken to record "abnormalities"' that were mentioned in the medical notes and that not being able to find a mention of these abnormalities indicates that these abnormalities were not present.This is a potentially problematic feature.In this context, I also have to indicate that I disagree with the statement of the authors that "there was no element of retrospective recall".All data collected from medical notes is "retrospective".
3) It read very little about actual data checking and validation, apart from what can be done around the data input processes itself.We have to accept that data abstraction from medical notes will have limitations (i.e., typically data completeness and quality inherently depend on the quality of the notes themselves) that cannot be overcome during the abstraction.
4) Given the ongoing developments of obstetric care and support for women before, during and after pregnancy, there is also a question about the relevance of some reported clinical findings.
The ultrasound results are a key example.I'm no expert but it is likely that ultrasound examination will have 'under-detected' abnormalities compared to ultrasound examination today.
4) A question that I think needs a bit more attention is the possible impact of selective inclusion of mothers and their babies as well as selective missingness of data.What work has been done to assess their impact and also what are the approaches to overcome potential selection bias issues?5) I would have liked to see a more detailed description of the data linkages that have been undertaken.Now, they are mentioned only once and that is a core admission, especially given that so much space has been assigned to details of abstracted data items that may be less relevant than the potential that data linkage can offer.
6) A critical reflection on what ALSPAC teaches about the future of longitudinal studies in the first place would have been welcome, especially given the move towards secondary use of routinely collected electronic data, data linkage and so on.

Wojciech Hanke
Nofer Institute of Occupational Medicine, Łódź, Poland The paper describes the process of obtaining information about the clinical aspects of labor to appropriately describe obstetrics health outcomes.
The descriptions are generally clear and allow for a detailed methodology presentation.
The only information, which might need some clarification is the one related to the definition of preterm delivery.As I understand it was based on a criterion of of less than 37 weeks of gestation.
Has there been any effort to distinguish spontaneous preterm delivery from the one resulting from medical indications?
Is the rationale for creating the dataset(s) clearly described?Yes This manuscript describes a prospective cohort study, including prenatal data regarding a large sample of mother-offspring dyads.Besides the relatively detailed information regarding the available data and the means of data collection, the authors propose to make this data available for researchers to analyze.Although there is very detailed information regarding the perinatal period, the external validity of the findings based on this cohort may be limited since this data was collected decades ago.Regarding the long term effects of certain early life exposures, it is unclear what long-term data is available for research, regarding both the mother and the offspring.
Is the rationale for creating the dataset(s) clearly described?Yes Are the protocols appropriate and is the work technically sound?Yes

Are sufficient details of methods and materials provided to allow replication by others? Yes
Are the datasets clearly presented in a useable and accessible format?Partly Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Perinatal and environmental epidemiology I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
Author Response 12 May 2022

Yasmin Iles-Caven
Dr Wainstock correctly points out that the information described was collected long ago.It is true that obstetric practice may have changed over time but, we feel that in many respects the data are likely to provide useful information of relevance to the present day.
Examples still of likely relevance include pre-eclampsia and placenta praevia.Of course there is the conundrum that if there are important long-term effects, they are unlikely to be evident for many years, by which time the particular exposure in question may not be in use.Nevertheless, it is important to document any long-term associations as they may be important to scientific understanding in the future.
Type of scan was coded as: (A) Clinic scan; (B) Dating scan; (C) Departmental scan; (D) Doppler scan; (E) Follow-up scan; Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).The article provides details regarding information abstracted from the obstetric medical records of mothers included in the Avon Longitudinal Study of Parents and Children (ALSPAC).The records cover pregnancy, labour, delivery and the first two weeks of the puerperium.This description of the cohort is intended to facilitate exploitation of the collected data for research into the perinatal antecedents of developmental and long-term outcomes for both mothers and babies.Recent publications based on the 50-year follow up the Collaborative Perinatal Project attest to the utility of such endeavors (see Hinkle et al.Lancet 2023).
Are the protocols appropriate and is the work technically sound?YesAre sufficient details of methods and materials provided to allow replication by others?YesAre the datasets clearly presented in a useable and accessible format?YesCompeting Interests: No interests were disclosed.Reviewer Expertise: Environmental epidemiology I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.Reviewer Report 03 May 2022 https://doi.org/10.21956/wellcomeopenres.18300.r43325© 2022 Wainstock T. This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Tamar Wainstock Department of Public Health, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel The long-term outcomes in the mothers and children who have taken part in the ALSPAC study are continuously updated.Details can be retrieved from the ALSPAC website: Explore data and samples | Avon Longitudinal Study of Parents and Children | University of Bristol.Information available includes medical and psychological outcomes, genetic and epigenetic data as well as the results of various psychometric and anthropometric measurements.The developing database includes details of the offspring of the original study children, thus enabling research into transgenerational associations.

Table 1 . The variables used and numbers of responses for each ultrasound scan.
[Admissions 6-33 are similarly available.]Theresult of the scan was characterised as normal or abnormal.'Normal' was coded if nothing out of the ordinary was noted, and 'Abnormal' if there was something of importance picked up on the scan including: breech or transverse presentation; date change by more than one week; low lying placenta; Table2).The data abstractors were instructed to record as text the reasons for each admission together with details of any treatment (including medications) given.The text has been keyed (but not yet coded) and is available on request.Results of standard measurements taken in hospital (blood pressures, weight, etc) have been added to the serial measurements (see Serial antenatal measurements made).The instructions were to include only one measurement per day and, if there were more, to select the one with the highest diastolic blood pressure.
mother in the puerperium).The measures recorded for each antenatal event include: (a) gestation in days; (b) place at which measurements were made, distinguishing between (i) community care, (ii) inpatient care, (iii) home visit, and (iv) consultant clinic; (c) maternal weight; (d) systolic and diastolic blood pressure; (e) proteinuria; (f) sites of oedema (if any); (g) haemoglobin level; and (h) level of glycosuria (Table3).The actual data for each measurement is described in more detail in http://www.bristol.ac.uk/alspac/external/documents/ALSPAC_Data_Dictionary.zip 1 and includes the extra data abstracted by Deborah Lawlor and team (see The extended dataset abstraction).

Table 2 . Table showing the variable numbers for the first nine admissions, the range of gestations at admission, the range in the number of days stayed, and the number of pregnancies involved.
[The admissions 10-18 continue in a similar format.] of glycosuria (DEL-1034), and first haemoglobin measurement (DEL_ 1047).For further information on this complete data set see: http://www.bristol.ac.uk/alspac/external/documents/ALSPAC_Data_Dictionary.zip 1

Table 3 . Numbers of pregnancies at each measurement event for which the following measurements were taken: A - place taken; B - gestation; C - maternal weight; D - blood pressure; E - level of proteinuria (recorded as nil; trace; +; ++; +++ or more; blood); F - oedema (coded as none; ankles only; hands only; face only; generalised; more than one site; and not otherwise stated (n.o.s)); G - level of haemoglobin (in g/dL); and H - level of glycosuria (recorded as nil; trace to +; ++; +++ or more; 0.25%; 0.5%; 1% or more). The first
five of 49 possible measurement events.The variable number for each measurement varies with the number of the measurement as shown above.For example, the systolic blood pressure is given by 'v1dab1g_systolic_bp*' where the asterisk denotes the event number above.] [

Table 4 . Features concerning the conception.
[N.B.The extended abstracted dataset also includes these data.]

Table 8 . Results of other standard laboratory tests during pregnancy.
*Data also available in extended abstracted dataset; a information on gestation of test and abnormal levels are available.

Table 9 . Procedures undertaken during pregnancy, prior to the onset of labour a .
*Also available in the full data set; a excluding ultrasound examinations.

Table 11 . The onset and process of labour: hospital admission, membrane rupture, induction, augmentation and caesarean section.
*Reasons given as text.

Table 12 . Drugs and procedures to induce or augment labour. Drug or procedure P no. Q no. No. with information No. receiving drug/procedure
*Described as text.<5 may equal zero.

Table 13 . Anaesthetics and analgesics administered to mother in labour or at caesarean section.
*Described as text.<5 may equal zero.

Table 14 . Other medication given in labour or at caesarean section.
*Described as text.<5 may equal zero.

Table 16 . Complications of, and procedures in, labour.
*Described in text.<5 may equal zero.

Table 18 . Medications taken in the postpartum period.
Also available in the extended abstracted dataset; a days after delivery the last blood pressure was recorded; b described as text.<5 may equal zero. *

the rationale for creating the dataset(s) clearly described? Yes Are the protocols appropriate and is the work technically sound? Yes Are sufficient details of methods and materials provided to allow replication by others? Yes Are the datasets clearly presented in a useable and accessible format? Yes Competing Interests:
No competing interests were disclosed.

have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

the rationale for creating the dataset(s) clearly described? Yes Are the protocols appropriate and is the work technically sound? Partly Are sufficient details of methods and materials provided to allow replication by others? No Are the datasets clearly presented in a useable and accessible format? No Competing Interests:
No competing interests were disclosed.Clinical epidemiology, data science, medical statistics, maternity, women's health cancer, healthcare performance assessment

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above. Version 1
This is an open access peer review report distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.